1. Field of the Invention
The present invention pertains to a running surface comprising a urethane elastomer layer having encapsulated particles of resilient material including solid urethane or rubber granules and an improved process for forming the surface.
2. Background Art
In the construction of synthetic surfaces for athletic fields such as running tracks for track and field events, jogging tracks, fence warning tracks and other artificial athletic playing surfaces, it is known to provide surfaces of solid urethane elastomer which may be applied over substrates including asphalt, concrete and other substructures. Such surfaces have proven to be superior in that they are not subject to environmental effects, and may be considered safer than natural playing surfaces or other types of man made surfaces for certain types of athletic events.
Indoor and outdoor running surfaces formed of a layer of poured urethane elastomer which cures to a solid resilient surface, have become quite popular for athletic runways or tracks. Urethane elastomers are relatively easy to handle in liquid form at average ambient temperatures are curable to a solid at ambient temperatures, and have relatively long life and weatherability. However, untextured or solid urethane elastomer surfaces lack the surface roughness desired for running surfaces, particularly of the type used for track and field events. Accordingly, heretofore it has been the practice in the art of constructing urethane runways and the like to provide a roughened surface by broadcasting particles and granules of solid urethane onto the surface after the liquid urethane has been poured or sprayed in place to form the runway base. The broadcasting of granules or surface coatings has been unsatisfactory in that adhesion of the granules to the urethane base is incomplete and the granules eventually break free or are partially broken away from the base. Accordingly, the track or runway surface again loses its attractive characteristics and resurfacing operations must be undertaken at frequencies which are costly.
Another problem with prior art applications of surface granules to increase traction on running tracks is that most techniques fail to provide a uniform distribution of granules. Accordingly, rough spots may develop in some areas of the running track whereas other areas may not have enough surface roughness.
Still another problem associated with prior art practice in constructing urethane elastomer running surfaces, pertains to the problem of maintaining a fairly uniform layer of the liquid urethane after it is poured on the substrate. Outdoor running tracks in particular, must be sloped to provide for suitable water runoff and indoor tracks are normally banked or sloped in the turns since they are shorter in overall length. Accordingly, the consistency of the liquid elastomer during application must be such that it then becomes difficult to pour and distribute. Alternatively, if the liquid elastomer is of the proper viscosity for suitable pouring and distribution, it will tend to run off the substructure leaving a thin coating along one longitudinal edge and a thicker coating along the opposite longitudinal edge of the track. Accordingly, the outside lanes of the track do not have the proper thickness.
The foregoing problems associated with the provision of artificial running surfaces and the like, and in particular, urethane elastomer running tracks, have been overcome by an improved surface composition in accordance with the present invention. The improved synthetic runway composition of the present invention is made particularly attractive due to an improved method of application of a urethane elastomer which includes the use of improved apparatus for mixing and applying the material comprising the surface. The composition of material, method and apparatus of the present invention is indicated to be capable of outstanding commercial success and has overcome a substantial number of problems heretofore known in the art of providing synthetic running surfaces.